Preparing paper internally sized with a fatty acid and wax



United States Patent N cw Jersey No Drawing. Filed Dec. 16, 1964, Ser. No. 418,863 Claims. (Cl. 9685) This application is a continuation-inpart of Garth, U.S. Serial No. 211,093, filed July 19, 1962, now abandoned.

This invention relates to sized paper having good resistance to penetration by various liquids, and the preparation of such paper.

One object of my invention is to provide paper having good resistance to penetration by various liquids, such as aqueous solutions and organic solvents such as alcohol. Another object of my invention is to provide a beatersized photographic paper base having good resistance to penetration by various liquids. A further object of my invention is to provide a method for preparing beater-sized paper having good resistance to penetration by various liquids. Still another object of my invention is to provide a method of preparing paper which features sizing the pulp with soap and then wax to provide a paper which has good resistance to penetration by various liquids. Other objects of my invention will appear herein.

These and other objects of my invention are accomplished by beater-sizing (or internally-sizing) paper with soap, thoroughly mixing the soap with the pulp, and then sizing the paper with wax. I have found that paper sized in accordance with my invention is highly resistant to penetration by various liquids, such as aqueous solutions in the pH range of 2.0 to 12.0, and organic solvents such as butyl alcohol. The method of sizing paper by the separate addition of soap and then wax in accordance with this invention provides paper having greater resistance to penetration by various liquids than would be expected from either the single additive effect of the combination, or the results obtained by the combined, simultaneous sizing of paper with soap and wax.

In accordance with my invention, an aqueous slurry of the pulp is prepared and a soap is added thereto in the desired quantity. The slurry of pulp and soap are then mixed, and wax, e.g. paraffin, is added in the form of an emulsion. Alum or aluminum chloride is then added to a pH below 6.0, preferably about 4.5. After further mixing, the pulp is formed into paper in accordance with conventional procedures.

My invention will be further illustrated by Examples 1 and 2. Examples 3-6 show the sizing of paper with sodium stearate, wax, rosin and Wax together with rosin. The papers obtained in accordance with Examples 1 and 3-6 were tested for resistance to penetration by various liquids and the results are shown in Table 1.

EXAMPLE 1 An aqueous slurry was formed consisting of 4% bleached sulfite pulp beaten to a Williams slowness of 30 seconds. 1.3%, based on the weight of the pulp, of commercial sodium stearate (normally containing the sodium salts of 6070% stearic acid, 20-30% palmitic acid and minor amounts of myristic, arachidic and/or behenic acids) was added to the dispersion which was then mixed for approximately 5 minutes and .5% of a 100% paraffin wax emulsion containing about 50% solids and a very small quantity of a surfactant (which emulsion, designated Paracol 505A, was obtained from Hercules Powder Company, Wilmington, Delaware) was added to the slurry with mixing. Alum was then added to a pH of 4.5. The pulp was then formed into paper in the usual manner, dried at 250 F. on drums for -20 3,24L968 Patented Mar. 22, 1966 ice seconds and calendered at about 140 F. The paper thus obtained was tested for resistance to aqueous solutions and various organic solvents. The results are shown in column 3 of Table 1.

EXAMPLE 2 The paper prepared in accordance with Example 1 was given a coating of barium sulfate dispersed in gelatin, and a gelatino-silver halide emulsion was coated thereover. The photographic emulsion had good adherence to the paper base, and the photographic material was satisfactory in all respects.

EXAMPLE 3 The procedure of Example 1 was followed except that the wax size was omitted. The paper which was obtained was tested for resistance to the penetration by aqueous solutions and organic solvents, and the results are shown in column 1 of Table 1.

EXAMPLE 4 The procedure of Example 1 was followed except that the sodium stearate size was omitted. The paper prepared in accordance with this procedure was tested for resistance to penetration by various liquids, and the results are shown in column 2 of Table 1.

*CP designates complete penetration.

Valley penetration is a measure of the resistance of a paper to penetration by liquid. It is determined by measuring the time that a sample of paper must be in contact (on both sides) Wih a glycerol solution containing a small amount of sodium chloride until it will conduct an electric current of 50 milliamperes.

Acid penetration is a measure of the resistance of a paper to penetration by acids which is determined by measuring, the time in seconds that a sample of paper must be in contact (on both sides) with an aqueous solution containing 7.5 grams sodium chloride and 625 cc. glacial acetic acid per liter of solution, until the paper will conduct an electric current of 20 inillianiperes.

Carbonate penetration is a measure of the resistance of a paper to penetration by a carbonate solution which is deter mined by measuring the time (in seconds) that a sample of paper must be in contact (on both sides) with a 5% aqueous solution of sodium carbonate, until the paper will conduct an electric current of 50 milliamperes.

Cobb size is the number of grams of solution absorbed by square cm. of the paper after 2 minutes contact with an aqueous solution containing 4% butyl alcohol. The excess solution is blotted off after contact with solution prior to determining the weight of the solution absorbed. Complete penetration indicates that the solution actually passed through the paper during the 2-minute contact period. This test is of particular importance in baryta coated photograhic paper since the baryto. contains a small amount of butyl alcohol to prevent foaming and to facilitate spreading of the baryta coating. If the butyl alcohol penetrates the paper, some baryta is carried with it, thereby causing a rough surface. This test, therefore, indicates whether a particular paper may be satisfactorily coated with baryta.

Developer pickup is the number of grams of developer absorbed by 1 square foot of paper after being passed into a developer solution and through a pair of small rollers to squeeze off the excess developer. lhe developer employed in the test contained phenidone, hydroquinone, sodium snlfite. potassium bromide, sodium hydroxide, and sequestering and wetting agents.

3 EXAMPLE The procedure of Example 1 was followed, except that the stearate and wax size was omitted and a 2% rosin size, based on the weight of the fiber, was substituted as an internal size. The results are shown in column 4 of Table 1.

EXAMPLE 6 The procedure of Example 1 was again followed, except that 2% rosin size, based on the weight of the pulp, was substituted for the sodium stearate size. The paper prepared in accordance with this procedure was tested for resistance to penetration by various liquids and the results are shown in column 5 of Table 1.

The resistance to penetration of the paper sized with sodium stearate and paraffin wax was greater than the penetration resistance expected from the additive effect of the sodium stearate size alone plus the wax size alone. The combination of sodium stearate and wax provided a more efiicient size for the paper than the rosin-wax sizing system, the latter having failed to provide good acid, alcohol or carbonate penetration resistance.

In carrying out my invention, paper is internally sized with a soap, such as alkali metal salts of fatty acids having from about 10 to 25 carbon atoms, e.g., sodium stearate and sodium palmitate. Especially useful results are obtained by sizing the paper with .4 to 4% soap, based on the weight of the fiber. Any suitable wax may be employed in this invention, such as paraffin wax, microcrystalline wax and the like. Advantageously, the paper is sized with .125 to 75% wax, based on the weight of the fiber. Highly satisfactory results are obtained by sizing with about 5% paraffin wax, based on the weight of the fiber. Preferably, the paraflin wax is used in the form of an aqueous emulsion containing a small amount of surfactant, such as a simple soap or a synthetic surfactant, for example a Triton (sulfonated ether, e.g., alkyl aryl polyether sulfonate).

When paper is prepared by beater sizing with the simultaneous addition of soap and wax, or by sizing first with wax and then with soap, the product does not have good resistance to liquid penetration. However, paper prepared in accordance with the invention by beater sizing with soap and then with wax has excellent resistance to liquid penetration. It appears that the soap becomes attached to the fiber, and the wax becomes attached to the soap. The time interval between the addition of the soap and the wax is important and must be of sufiicient duration to allow the soap to attach to the fibers. This time interval depends largely on the efficiency of agitation of the pulp. In large batch operations using good agitation, it is preferred to have an interval of at least 3 minutes although with more efficient agitation, this time could be reduced. However, systems may be employed in which a small volume of pulp is well agitated (such as continuously passing the pulp through a small cylinder, agitating well and introducing soap upstream and wax downstream) wherein the time interval may be as short as about 2 or 3 seconds. The wax may be added to the pulp as soon as the soap has become attached to the fibers, or at any suitable time thereafter, such as one to one and one-half hours after the addition of the soap. Once the soap has been thoroughly mixed with the pulp, the time at which the wax is added is not critical.

In sizing the pulp in accordance with my invention, I prefer to precipitate the size at a pH below 6, preferably at about 4.5, by the addition of alum, aluminum chloride, or other compositions which do not interfere with the size.

The invention has been described in detail with particular reference to preferred embodiments thereof but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

Iclaim:

1. In the method of making paper by preparing an aqueous slurry of pulp, forming a web from the slurry and removing water, the method of internally sizing the paper which comprises added to the aqueous slurry of pulp about 1.3%, based on the weight of the pulp, of a compound selected from the group consisting of sodium stearate and sodium palmitate; mixing the slurry for approximately 5 minutes; mixing with the pulp about .5%, based on the weight of the pulp, of a paraffin wax emulsion containing about 50% solids and a small quantity of surfactant; adding alum to the aqueous pulp slurry to obtain a pH of about 4.5; and forming the pulp into paper.

2. In the method of making paper by preparing an aqueous slurry of pulp, forming a web from the slurry and removing water, the method of internally sizing the paper which comprises adding to the aqueous slurry of pulp, in separate steps and in the order given, .4 4%, based on the weight of the fiber in the slurry, of a soap selected from the group consisting of sodium stearate and sodium palmitate, and .125-.75%, based on the weight of the fiber in the slurry, of parafiin wax, the wax being added to the slurry after the soap has been thoroughly mixed therewith; reducing the pH of the slurry to below 6.0; and, forming the pulp into paper.

3. In the method of making paper by preparing an aqueous slurry of pulp, forming a web from the slurry and removing water, the method of internally sizing the paper which comprises adding to the aqueous slurry of pulp, in separate steps and in the order given, .44%, based on the weight of the fiber in the slurry, of an alkali metal salt of a fatty acid having from 10-25 carbon atoms, and .125.75% wax, based on the weight of the fiber in the slurry, the wax being added to the slurry after the salt has been thoroughly mixed therewith; precipitating the size; and, forming the pulp into paper.

4. Paper highly resistant to the penetration of liquids sized in accordance with the method of claim 3.

5. A photographic element comprising a photographic silver halide emulsion coated on a paper highly resistant to the penetration of liquids sized in accordance with the method of claim 3.

References Cited by the Examiner UNITED STATES PATENTS 1,234,315 7/1917 Eising l62172 1,727,003 9/1929 Clapp 162172 2,629,295 2/1953 Richter et al. 162-179 DONALL H. SYLVESTER, Primary Examiner. 

3. IN THE METHOD OF MAKING PAPER BY PREPARING AN AQUEOUS SLURRY OF PULP, FORMING A WEB FROM THE SLURRY AND REMOVING WATER, THE METHOD OF INTERNALLY SIZING THE PAPER WHICH COMPRISES ADDING TO THE AQUEOUS SLURRY OF PULP, IN SEPARATE STEPS AND IN THE ORDER GIVEN, .4-4%, BASED ON THE WEIGHT OF THE FIBER IN THE SLURRY, OF AN ALKALI METAL SALT OF A FATTY ACID HAVING FROM 10-25 CARBON ATOMS, AND .125-75% WAX, BASED ON THE WEIGHT OF THE FIBER IN THE SLURRY, THE WAX BEING ADDED TO THE SLURRY AFTER THE SALT HAS BEEN THOROUGHLY MIXED THEREWITH; PRECIPITATING THE SIZE; AND, FORMING THE PULP INTO THE PAPER.
 5. A PHOTOGRAPHIC ELEMENT COMPRISING A PHOTOGRAPHIC SILVER HALIDE EMULSION COATED ON A PAPER HIGHLY RESISTANT TO THE PENETRATION OF LIQUIDS SIZED IN ACCORDANCE WITH THE METHOD OF CLAIM
 3. 